Conductivity-determining type impurity dopant-comprising compositions, such as borosilicates and phosphosilicates, are used extensively for doping semiconductor substrates, such as to form pn junctions and contact areas. In some applications, the doped silicates are designed to perform other functions such as to serve as barrier regions, insulation regions, etc. Typically, the doped silicates are coated on the semiconductor substrates and then are thermally treated, such as by rapid thermal annealing, to cause the dopants to diffuse into the substrates. These applications typically require defect-free and thicker precursor coatings on the substrates.
However, it is difficult to achieve defect-free and thicker precursor coatings with conventional doped silicates, particularly on semiconductor wafers used in applications, such as solar cells, that have a rougher topology than semiconductor wafers used for semiconductor devices. When applied to a semiconductor wafer, which typically has a surface topology with peaks and valleys, a conventional precursor coating tends to be thin on the peaks and accumulate in the valleys. This nonuniformity in thickness causes the coating to crack, leading to doping anomalies. Accordingly, there is a need for dopant-comprising compositions that form conformal precursor coatings to minimize cracking.
In addition, precursor coatings formed from prior art doped silicates, such as conventional sol-gel doped silicates, tend to adsorb moisture over time. Adsorption of water in the precursor coating leads to particle defects and phase separation in the coating. Accordingly, there is a need for moisture resistant dopant-comprising compositions that provide suitable doping concentrations while resisting moisture adsorption.
Thus, it is desirable to provide moisture-resistant conductivity-determining type impurity dopant-comprising compositions for forming doped regions in semiconductor substrates. In addition, it is desirable to provide conductivity-determining type impurity dopant-comprising compositions that form conformal precursor coatings on semiconductor substrates. It also is desirable to provide methods for fabricating such compositions. Moreover, it is desirable to provide methods for forming doped regions using such compositions. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.